Oscillator



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OSCILLATOR 2 Sheets-Sheet 2 Filed Aug. 25. 1958 v. @Fm

EARL T /RETO/V HANS 6."KRAU$S INVENTOR` A TTOHNE'Y United States PatentOice 3,011,354 Patented Dec. 5, 1961 3,011,354 OSCILLATOR Earl T.Ireton, Audubon, NJ., and Hans G. Krauss, Kalamazoo, Mich., assignors,by mesne assignments, to

Boeing Airplane Company, Seattle, Wash., a corporation of Delaware FiledAug. 25, 1958, Ser. No. 756,999 Claims. (Cl. 74-25) This inventionrelates to oscillators for inducing vibrations in structural units andmore particularly to an oscillator for inducing a sinusoidal vibrationof controlled force and frequency in an aircraft.

It is a primary object of the invention to provide an oscillator capableof producing relatively high vibratory forces at relatively lowfrequencies wherein those forces are generated by hydraulically actuatedmeans which follow or are controlled by a relativelyk low poweroscillating system.

It is a further object of the invention to provide an oscillator whichgenerates a constant vibratory force throughout a range of operatingfrequencies.

It is a further object to provide such oscillator with means forchanging the generated vibratory force independently of the frequencywhereby different constant vibratory forces may be generated throughoutthe operating frequency range.

It is a still further object to provide an oscillator having ahydraulically actuated oscillating mass, with automatic means forvarying the oscillating frequency thereof in response to manuallycontrolled changes in the amplitude of displacement of the mass in suchmanner as to generate. a constant vibratory force. A still furtherobject is to provide the oscillating mass with acceleration responsivemeans to cause automatic shut-down in the event a predeterminedacceleration is exceeded.

Other objects of the invention, as well as the advantages thereof, willbecome apparent from the following description when read in conjunctionwith the accompanying drawings in which:

FIG. 1 is a plan view partly in section of a preferred embodiment of anoscillator constructed in accordance with the present invention;

FIG. 2 is a partial end view showing the Scotch yoke assembly by whichthe hydraulic control is driven;

FIG. 3 is an enlarged partial view taken along lines 3-3 of FIG. l; and

FIG. 4 is a diagram of the electrical control system.

Referring to FIG. l, the oscillator is shown to include a basecomprising beam members 11, 12 and 13 connected together by cross beams14, and 16. The base 10 is mounted by means of bolts 17 or the like, tothe structure in which it is desired to induce vibrations. Slide rods 18and 19 are connected at their opposite ends to the cross beams 14 and 15and slidably support a mass 20 which is reciprocated back and forth onthe slide rods 18 and 19 by a hydraulic actuator 21. The actuator 21comprises a cylinder 22 bolted or otherwise secured to the base 10 bymeans not shown, and a piston 23 connected to the mass by means of thepiston rod 24 extending through one end of the cylinder 22. A secondpiston rod 25 extends through the other end of the cylinder 22 and haspivotally mounted on the extremity thereof a link 26, in turn pivotallyconnected to the spool element 27 of the actuator control valve 28.Pressure uicl from a source not shown is supplied to the control valve28 through a line 29 containing a solenoid actuated on-ofi valve 30,while return ow to a reservoir not shown is through line 31. Ducts 32and 33 cooperate-with the control valve 28 for communicating pressurefluid to the end chambers 34 and 35 of the actuator 21.

A link 36 is pivotally connected at one end to the link 26 and at itsother end is pivotally connected to one end of a lever 37 pivotallymounted upon the cross beam 16. A link 38 connects the lever 37 with onearm of a bellcrank 39 pivotally mounted upon the beam member 12, whilethe other arm of the bellcrank 39 is connected to Scotch yoke assembly40 by means of a ylink 41. As shown in FIG. 2, guide members 42 and 43extend through the slotted cross-head 44 of the assembly 40 to limit itsmotion to one plane.

A variable speed power source or motor means, preferably ,an A.C.electric motor 45 provided with a D.C. field control, is mounted on thebase 10 and drives by means of a belt 46 and pulleys 47 and 48 a shaftassembly 49. The assembly 49 is rotatably mounted upon the base 10 bymeans of bearings l50 and 51, and comprises an outer hollow shaft 52having a bifurcated end portion 53 on which are carried bevel gears 54and 55. These f gears mesh with a bevel gear 56 adapted for rotationrelative to the outer shaft 52 by means of an inner shaft 57 driven by areversible motor 58 contained within and rotatable with the outer shaft.

The gears 54 and 55 are provided with threaded shafts 59 and 60,respectively, which extend radiallyI out through the end portion 53 ofthe shaft 52 and upon which are mounted a crank mechanism 61 and acounter-weight 62. The crank mechanism 61 is provided with a pinextension 63 adapted to be received in the slide block 64 of the Sctochyoke assembly 40. Lugs 65 and 66 on the extremity of the end portion 53of shaft 52 embrace the sides of the crank mechanism 61 and thecounter-weight 62, while a slot not shown in the crank mechanism isadapted to receive a mating pin 67 provided on the counter-weight toprevent, together with the lugs 65 and 66, any misalignment or twistingof those two parts.

The arrangement just described is such that rotation of the gears 54 and55 by the gear 56 causes opposite displacement of the crank mechanism 61and the counterweight 62 to thereby substantially maintain the balanceof the rotating parts. The displacement of the crank mechanism 61produces an eccentricity between the axes of the pin 63 and the shaft 52whereby rotation of the shaft assembly is converted to a pure harmonicmotion of the crosshead 44 of the Scotch yoke assembly and through theassociated control valve linkage, to the valve spool element 27. It isreadily apparent that the amount of eccentricity between the pin 63 andthe shaft 52 will determine the amount of displacement of the valvespool element and hence the amount or amplitude of displacement of thepiston 23 and the mass 20 attached thereto. The frequency of thatdisplacement is of course determined by the rotationl speed of thedriving motor 45.

A definite mathematical relationship exists between the inertia force ofa vibrating mass, the frequency of vibration and the amplitude ofdisplacement of the mass. For a constant mass and force, it can be shownthat the frequency is proportional to the square root of the reciprocalof the amplitude, or conversely, the amplitude is proportional to thereciprocal of the square of the frequency. Accordingly, if the amplitudeof displacement is changed, there must also be a charge in the frequencyin accordance with the relationship just stated if the force is toremain constant. Means for automatically changing the frequency inresponse to changes in the amplitude of displacement so as to maintain aconstant vibratory force are shown in FIG. 4.

As shown therein, the electric motor 45 drives a tach generator 68, thefunction of which is to generate a voltage proportional to itsrotational speed. This voltage is impressed, by means of the conductors69 and 70 and the slip rings 71 carried by the shaft assembly 49, acrossa potentiometer 72 mounted upon the end portion 53 of the outer shaft52. An associated wiper 73, mounted upon the crank 61 and connected by aconductor 74 and one of the slip rings 71 to an amplifier 75, servesasmeans for taking off a voltage proportional to the wiper position andhence the eccentricity between the axes of the pin 63 and the shaft 52.This voltage, proportional to the rotational speed of the shaft assemblyand the eccentricity of the crank mechanism, is amplified by theamplifier 75 and the amplified signal therefrom is compared by arectifying network 76 with a reference voltage supplied by a D.C. sourceimpressed across a potentiometer 77 having an associated manuallycontrolled or positioned wiper 78 connected to the network 76. Thedifference between the reference signal and the amplified signal fromthe amplifier 75, is amplied by an amplifier 79 and fed to regulatingmeans 80, the purpose of which will be explained hereinbelow.

The primary D.C. source of power 81 is connected through a switch 82 toan invertor 83, the function of which is to convert the D.C. power to a400 cycle, 115 volt A.C. This A.C. power is utilized to energize,through connections shown in part, and thereby cause operation of themotor 45. Power from the invertor 83, as controlled by the regulator 80,is also applied to a rectifier 84, the output from which is fed directlyto the control field of the motor 45 to thereby control the rotationalspeed of that motor. Closing the switch 82 also completes a circuitthrough an accelerometer switch 85 mounted upon the mass 20, and thesolenoid of the solenoid actuated valve 30 in series therewith. Theaccelerometer switch 85 is of the type which will open the circuit if apredetermined acceleration is exceeded whereby the solenoid of the valve30 will be deenergized which in turn will permit the valve to close andcut off the ow of pressure uid to the control valve 28 therebysuspending operation of the hydraulic actuator 21.

The D.C. source of power is connected also through a double throw switch86 and by means of slip rings 87 to the reversible electric motor 58whereby the motor 58 may be energized to cause operation thereof ineither direction.

In operation, when the motor 58 has been energized to position the crankpin 63 eccentric to the axis of the shaft assembly 49, closing of theswitch 82 causes actuation of the valve 30 to permit the supply ofpressure fluid to the control valve 28, and causes operation of themotor 45. The shaft assembly 49 is thus caused to rotate and through theeccentric crank pin 63 and Scotch yoke assembly 40 an up and down motionis imparted to the link 41. When the link 41 moves downwardly thebellcrank 39 is caused to rotate in a clockwise direction, which throughlink 38, lever 37, link 36 and link 26 moves the spool element 27 to theleft as shown. In this position, pressure fluid is admitted to the endchamber 35 through duct 32 which causes the piston 23 and mass attachedthereto to move to the left. Piston rod 25 is carried to the left andcarries with it the lower end of the link 26 whereby the link 26 isrotated in a clockwise direction to return the spool element 27 to itsneutral position. Similarly, when the link 41 moves upwardly as theshaft assembly continues to rotate, the spool element 27 is moved to theright thereby directing pressure uid through duct 33 to the end chamber34 which causes the piston 23 to move to the right. This again causesrotation of link 26 and the return of the spool element 27 to itsneutral position.

It is apparent that the speed of operation of the motor 45 is dependentupon the position of the wipers 73 and 7,8. When the speed of operationis such that the output signal from the amplifier 75 is balanced by Athereference signal taken off the potentiometer 77, the speed of the motorwill remain constant. However, any change in the position of the crankmechanism and hence the position of the wiper 73, will produce adifferent signal across the conductors 70 and 74, which signal whenamplified by the amplifier 75 and compared with the reference signaltaken off the potentiometer 77 will produce a signal at the amplifier79. This signal, when amplified and fed to the line regulator 80, willcause either an increase or decrease in the power supplied to thecontrol field of the motor 45, depending upon the direction of thesignal, and hence either an increase or decrease in the speed of themotor until the output signal from the amplifier is again balanced bythe reference signal. Similarly, any change in the position of the wiper78 to change the reference signal will produce a signal at the amplifier79, which results in an increase or decrease in speed of the motor 45,depending upon the direction of the signal, until the output signal fromthe amplifier 75 is again balanced by the reference signal.

Although shown and described in what is believed to be the mostpractical and preferred embodiment, it is apparent that departurestherefrom will suggest themselves to those skilled in the art and may bemade without departing from the spirit and scope of the invention. Wetherefore do not wish to restrict ourselves to the particular form ofconstruction illustrated and described, but desire to avail ourselves ofall modifications that may fall within the scope of the appended claims.

Having thus described our invention, what we claim is:

1. An oscillator for producing vibrations comprising a mass adapted foroscillating motion, a hydraulic actuatorv` connected to said massand'provided with-acontrol valve, crank mechanism having a variablethrow and operatively connected to said control valve, motor means forrotatably driving said crank mechanism, means for generating a firstsignal proportional to the rotative speed of said motor means and meansfor generating a second signal proportional to the throw of said crankmechanism, a reference signal, means for comparing said first and secondsignals with said reference signal, and means responsive to thedifference in the signals so compared for controlling the rotative speedof said motor means.

2. An oscillator for producing vibrations comprising a mass adapted foroscillating motion, a hydraulic actuator connected to said mass andprovided with a control valve. crank mechanism having a variable throwand operatively connected to said control valve, manually controlledmeans for varying the throw of said crank mechanism, motor means forrotatably driving said crank mechanism, means for generating a firstsignal proportional to the rotative speed of said motor means and meansfor generating a second signal proportional to the throw of said crankmechanism, a reference signal, means for comparing said first and secondsignals with said reference signal, and means responsive to thedifference in the signals so compared for controlling the rotative speedof said motor means.

3. An oscillator for producing vibrations comprising a mass adapted foroscillating motion, a hydraulic actuator connected to said mass andprovided with a control valve, a second valve for controlling the fiowof pressure fluid to said control valve, acceleration responsive meansmounted upon said mass for controlling said second valve, crankmechanism having a variable throw and operatively connected to saidcontrol valve, motor means for rotatably driving said crank mechanism,means for generating a first signal proportional to the rotative speedof said motor means and means for generating a second signalproportional to the throw of said crank mechanism, a reference signal,means for comparing said first and second signals with said referencesignal, and means responsive to the difference in the signals socompared for controlling the rotative speed of said motor means.

4. An oscillator for producing vibrations comprising a mass adapted foroscillating motion, a hydraulic actuator connected to said mass andprovided with a control valve having a link operatively connected tosaid hydraulic actuator to provide4 a follow-up motion to said controlvalve, crank mechanism having a variable throw operatively connected tosaid link for imparting reciprocating motion to said control valve,motor means for rotatably driving said crank mechanism, means forgenerating a first signal proportional to the rotative speed of saidmotor means and means for generating a second signal proportional to thethrow of said crank mechanism, a Ireference signal, means for comparingsaid rst and second signals with said reference signal, and meansresponsive to the dilerence in the signals so compared for controllingthe rotative speed of said motor means.

5. Apparatus as claimed in claim 4 characterized by the provision of asecond valve'for controlling the ow of pressure fluid to said controlvalve and acceleration responsive means mounted upon said mass forcontrolling said second valve.

References Cited in the ile of this patent UNITED STATES PATENTS OTHERREFERENCES Product Engineering, Hydraulic Vibrators, Dec. 9, 1957, pages9498.

